ES2234925T3 - PROPYLENE COPOLYMER FOAMS. - Google Patents

Abstract

A foam comprising a propylene copolymer material comprising at least 50 weight percent of units derived from propylene, based on the total propylene copolymer material, and units derived from ethylenically unsaturated comonomers and having a melt flow rate in the range of from 0.5 to 8 g/10 min, a melt strength of at least 5 cN, and a melt drawability of at least 20 mm/s, process for making a foam using such a propylene copolymer material, process for making a foam in the form of thermoplastic foam beads using such a propylene copolymer material, and an expandable composition comprising such a propylene copolymer material.

Description

Propylene copolymer foams.

The production of foams from polymers of Propylene is hindered by the low viscosity and elasticity of the melt of these polymers. Attempts to use resins of standard propylene to obtain foams result in normally a loss of stability of foam bubbles or of the foam cell walls and consequently foams of Poor quality or collapsed.

DeNicola et al . described in US Pat. No. 5,605,936 that propylene polymers of increased melt toughness can be obtained by irradiation of the polymers. However, when such polymers are mixed with elastomers to obtain better impact resistance, the toughness of the melt suffers. Irradiation of heterophasic (or impact) resins by conventional radiation methods resulted in resins of improved melt toughness, but also severe gelation and a high degree of crosslinking occurs, which is undesirable in foaming applications (column 1 , lines 42-58 and Control Examples 6-8). DeNicola et al . they suggest providing foams from a composition of three different components, including high levels (30-80 weight percent) of ethylene-propylene copolymer elastomer whose mixture is typically subjected to irradiation.

In US Pat. No. 5,348,795 Park describes low density open cell foams that are stable dimensionally and are typically prepared from high strength propylene homopolymers of the melt or random copolymers of high mass tenacity propylene cast.

In the US patent application 09 / 133,576 in process with this, filed on August 13, 1998 and international patent WO-99/10424 describes the in situ modification of the rheology of polyolefins applied to, among others, polypropylenes and mixtures of polypropylenes with elastomers, resulting in polypropylenes that have advantageous melt processing properties. Foams are mentioned among the possible uses and final applications of such modified rheology propylene polymers. However, nothing else is shown about suitable materials for foams or foam properties.

There is still a demand for foams other than fragile and have good low damping properties temperature. It is also desirable to obtain such foams using Simple foaming procedures and equipment.

Compendium of the invention

The invention in one aspect provides a foam comprising a propylene copolymer material comprising at least 50 percent by weight of units derived from propylene, based on the total weight of the propylene copolymer material, and units derived from ethylenically unsaturated comonomers and that they have a melt flow rate in the range of 0.5 to 8 g / 10 min, a melt toughness of at least 5 cN, and a capacity of stretching of the melt of at least 20 mm / s.

In addition, a procedure is provided for obtaining a foam, a method comprising converting a propylene copolymer material comprising at least 50 per percent by weight of units derived from propylene, based on the Total propylene copolymer material, and units derived from ethylenically unsaturated comonomers and having a flow rate of melt in the range of 0.5 to 8 g / 10 min, a toughness of the melt of at least 5 cN, and a stretching capacity of the melt of at least 20 mm / s, optionally mixed with a nucleating agent, in a polymer melt, introduce, to a high pressure, at least one blowing agent in the dough polymer melt to form a foamable gel, cool the gel foamable and extrude the foamable gel in a region of lower pressure to form a foam

According to a further aspect of the invention, provides a procedure to obtain a foam in the form of thermoplastic foam beads, method comprising converting a propylene copolymer material comprising the minus 50 percent by weight of units derived from propylene, based on the total propylene copolymer material, and units derived from ethylenically unsaturated comonomers and having a melt flow rate in the range of 0.5 to 8 g / 10 min, a melt toughness of at least 5 cN, and a capacity of stretched at least 20 mm / s, optionally mixed with an agent nucleating, in a polymer melt, cool and granulate the polymer melt to form discrete particles of resin, create a suspension by dispersion of the particles of resin in a liquid medium in which they are substantially insoluble, introduce, at high temperature and pressure, at least a blowing agent in the suspension to form particles of resin that have a blowing agent incorporated therein, and quickly download the product in an atmosphere that promotes Product conversion into foam beads.

The invention additionally provides a expandable composition comprising a copolymer material of propylene comprising at least 50 percent by weight units propylene derivatives, based on the total weight of the material propylene copolymer, and units derived from comonomers ethylenically unsaturated and having a melt flow in the range of 0.5 to 8 g / 10 min, a toughness of the dough melt of at least 5 cN, and a dough capacity molten at least 20 mm / s, optionally mixed with an agent Nucleant and a blowing agent.

Detailed description of the invention

As used herein, the term "melt toughness" and "ability to stretched "refer to the properties of the melt of the polymer and are measured at 190 ° C according to the following procedure. Measure  of the melt toughness using a capillary rheometer fitted with a 20: 1 diameter 2.1 mm nozzle with an angle of input of approximately 45 degrees. After balancing the samples at 190 ° C for 10 minutes, the piston is passed to a speed of 2.54 cm / min (1 in / min). The standard temperature of test is 190 ° C. The sample is uniaxially dragged to a set of spaces between acceleration rollers located 100 mm by under the nozzle, with an acceleration of 2.4 mm / s2. The force required traction is recorded as a function of the speed of winding of the drag rollers. Traction force reached during the test (at break) is defined as the toughness of the melt and is expressed in centiNewtons (cN). Speed of the steering wheel limiting the breakage is the stretching capacity of the melt and is expressed in units of mm / s. In the case of a Polymer melt exhibiting stretching resonance, the traction force and flywheel speed of the beginning of the stretching resonance was taken as the melt toughness and stretching capacity, respectively.

As used herein, the term "melt flow rate" refers to the melt flow rate of the polymer measured according to ASTM D 123 8L method, at a temperature of 230 ° C under a weight of 2.16 kg and is expressed in g / 10 min.

The density of the resin (polymer) was determined by ASTM D-792, using the principle of Archimedes of main displacement.

The gel content was determined by xylene extraction - ASTM procedure "A" D-2765 to measure the degree of crosslinking of the polymer. The samples were immersed in xylene to extract what It was not a gel (or crosslinked). After extraction, the sample a It was then dried and weighed. The resulting data is They turned into percent gel.

The propylene copolymer material used in foams of the present invention comprises at least 50 percent by weight of units derived from propylene, based on the total weight of propylene polymer and units derived from comonomers ethylenically unsaturated, said copolymer material having  propylene a melt flow rate in the range of 0.5 to g / 10 min, a melt toughness of at least 5 cN, and a capacity of stretching of the melt of at least 20 mm / s. Preferably, the propylene copolymer material has a melt flow rate in the range of 0.6 to 5 g / 10 min, a melt strength of at least 7 cN, and a capacity of stretching of the melt of at least 30 mm / s, more specifically a melt flow rate in the range of 0.6 to 3.5 g / 10 min, a melt toughness of at least 10 cN, and a capacity of stretching of the melt of at least 40 mm / s. Current copolymer materials have processability relatively better, that is, a melt flow rate more raised, at the same toughness of the melt and, thus, foams can be produced from the materials of copolymer at higher production rates than possible with the materials of the prior art. A mass flow melted below the lower limit, quantities are required relatively high energy for the production of materials from foam, then resulting in a more production cost tall.

The propylene copolymer material used in the foams of the present invention generally have a hardness Rockwell measured according to DIN 50103 of less than 90 HRC, and more preferably less than 85 HRC.

The ethylenically unsaturated comonomer of propylene copolymer material is preferably selected from the group consisting of ethylene, 1-olefins of C_ {4} -C_ {10} and dienes of C_ {4} -C_ {10}. The copolymer material of propylene in the foams present preferably comprises a random copolymer of propylene. Alternatively, the material of propylene copolymer preferably comprises a continuous phase of a propylene homopolymer or a propylene copolymer at random or block and disperses evenly in it a phase elastomeric The latter material also refers to both a heterophasic or impact copolymer. The copolymer material of propylene is preferably a propylene copolymer material of modified rheology.

As used herein, the terminology "modification of rheology or rheology modified "means change in polymer resistance melted to flow. The resistance of the polymer melt to flow is indicates by (1) the coefficient of growth of the tension of tensile and (2) shear viscosity coefficient dynamic. The tensile stress growth coefficient, E +, is measured during the beginning of the uniaxial extensional flow, by media according to those skilled in the art, as described by J. Meissner in Proc. XIIth International Congress on Rheology, Quebec, Canada, August 1996, pages 7-10 and by J. Meissner and J. Hostettler, Rheol. Minutes, 33, 1-21 (1994). The dynamic shear viscosity coefficient is measured with sinusoidal shear flow experiments of small amplitude by means according to those skilled in the art, as described by R. Hingmann and B.L. Marczinke, J. Rheol. 38 (3), 573-87, 1994.

The known methods of modifying the Rheology include irradiation treatment or treatment chemical with coupling or branching agents or a combination of such treatments. The preferred procedure for produce the modified rheology propylene polymer material  involves coupling the polymer material using an agent of coupling. The coupling reaction is carried out at through reactive extrusion or any other method that is capable of mixing the coupling agent with the polymeric material and add enough energy to cause a reaction of coupling between the coupling agent and the material polymeric Preferably, the procedure is carried out in a single vessel such as a melt mixer or a polymeric extruder, as described in the patent application from the USA 09 / 133,576, filed on August 13, 1998 (corresponding to WO-99/10424) that vindicates the benefit of the provisional US application Do not. 60 / 057,713, filed on August 27, 1997, both are incorporated here as a reference in its entirety. The term extruder tries include its broadest meaning and includes devices such as a device that extrudes pellets, as well as an extruder that Produces the extrudate to form it in films, articles blow molded, profile articles and extruded sheets, foams and other items. The resulting polymer of this Preferred rheology modification is a "coupled polymer" resulting from a coupling reaction. A coupled polymer differs from a crosslinked polymer in that the coupled polymer is thermoplastic and has a low gel level.

Other less preferred treatments of rheology modification are described, for example, in the US patents 4,714,716, 4,916,198, 5,883,151, 5,266,643 and 5,929,127 (which are incorporated herein by reference in its entirety). You can also use combinations of treatments rheology modification.

Advantageously, the copolymer materials of propylene which are used to produce foams according to the present invention are obtained by rheology modification and preferably by coupling the impact propylene copolymers or random copolymers of propylene known to provide propylene copolymer materials having the properties desired.

The random copolymers suitable for the rheology modification include a propylene copolymer and one or more olefins selected from the group consisting of ethylene, 1-C 4 -C 10 olefins, and dienes of C_ {4} -C_ {10}, provided that when said olefin is ethylene, the polymerized ethylene content maximum is less than about 20% by weight, when said olefin is a 1-olefin of C 4 -C 10, the maximum polymerized content thereof is less than about 20% by weight and when said Olefin is C 4 -C 10 diene, its content maximum polymerized is less than about 20% by weight. Plus preferably, the random copolymer is a random copolymer of ethylene-propylene that has 1 to 10 percent in weight of units derived from ethylene, more preferably the random copolymer is a random copolymer of ethylene-propylene that has 1 to 5 percent in weight of units derived from ethylene.

Appropriate impact propylene copolymers for the modification of the rheology include polymeric materials in which a propylene homopolymer or a copolymer of random or block propylene is the continuous phase and a dispersed elastomeric phase uniformly in it. The experts in the technique recognize that this elastomeric phase may also contain crystalline regions, which, for the purposes of the present invention, They are considered part of the elastomeric phase. The copolymers of Impact propylene can be prepared by a procedure inside the reactor or physically mixing their constituents In a preferred embodiment, the copolymers of Impact propylene are formed by mixing in the reactor, advantageously in a two or multi stage procedure, which optionally involves a single reactor, taking place at least two procedural steps therein, or optionally reactors multiple. The impact copolymers produced in the reactor since a physical mixing stage is not required and is more easily obtain a finer and relatively distributed better elastomer in the continuous phase and at an energy cost Minor.

The impact propylene copolymers and at random that are used for rheology modification are commercially available and are well known to experts in the technique, for example, as described by E.P. Moore, Jr in Polypropylene Handbook, Editorial Hanser, 1996, pages 98-98, 211-222 and 244-249 and in US Pat. 3,893,989 and 4,123,802.

Advantageously, the propylene copolymer of impact for rheology modification has at least about 5 weight percent, preferably at least about 9 per weight percent, more preferably at least about 13 per weight percent of an elastomeric phase based on the total weight of the  impact propylene copolymer. Preferably, the phase Elastomeric is less than about 45 percent by weight, more preferably less than about 40 percent in weight, most preferably less than about 38 percent in weight, of the total weight of the impact propylene copolymer. A higher elastomer content decreases the transition point ductile-fragile at lower temperatures and increases additionally the impact properties.

When the copolymer phase continues Impact propylene is a homopolymer propylene polymer and the elastomeric phase consists of a copolymer or terpolymer that contains monomer units derived from ethylene, the copolymer of impact propylene preferably contains at least about 5 percent by weight, more preferably at least about 7 percent by weight, most preferably at least about 9 per weight percent of -CH2CH2- units derived from monomer of ethylene based on the total weight of the impact copolymer of propylene Preferably, such a propylene impact copolymer it contains less than about 30 percent by weight, more preferably less than 25 percent by weight, most preferably less than about 20 percent by weight units of -CH2CH2- ethylene monomer derivatives based on the total weight of the propylene impact copolymer. Most preferable, this Propylene impact copolymer is a material produced in the reactor.

The continuous phase of the impact copolymers of Propylene is typically a homopolymer of propylene or a random copolymer of propylene, more typically a polymer of homopolymer propylene. The propylene polymer can be obtain using a Ziegler-Natta catalyst, a restricted geometry catalyst, a metallocene catalyst, or any other suitable catalyst system. When the polymer of propylene obtained from the continuous phase is a homopolymer of propylene, the crystallinity of the propylene polymer, as determined by differential scanning calorimetry, it is preferably at least about 50 percent, more preferably at least about 55 percent, most Preferable of about 62 percent. The methods for determine the percent crystallinity using a differential scanning calorimetry are known to some expert in the art, for example, as described by E.P. Moore, Jr in Polypropylene Handbook, Hanser publications, 1996, pages 124-128. The propylene impact copolymer is characterized by impact resistance (ASTM D256, Impact with IZOD notch, 23 C) of at least 60 J / m, preferably at at least 80 J / m, and most preferably at least 100 J / m.

According to the modification treatment of preferred rheology, the coupling treatment, a copolymer Random propylene or propylene impact copolymer are made react with a polyfunctional compound capable of reactions of insertion in the C-H links. Such compounds polyfunctional have at least two, preferably 2, groups functional capable of forming reactive groups, which are capable of C-H insertion reactions. The experts in the technique are familiar with insertion reactions in C-H and the reactive groups capable of said reactions. For example, the carbenes as generated from diazo compounds, as mentioned in Mathur, N.C .; Snow, M.S .; Young, K.M., and Pincock, J.A .; Tetrahedron, (1985), 41 (8), pages 1509-1516, and nitrenes as generated from azides, as mentioned in Abramovitch, R.A .; Chellathurai, T .; Holcomb, W.D; McMaster, I.T .; and Vanderpool, D.P .; J. Org. Chem., (1977), 42 (17), 2920-6, and Abramovitch, R.A., Knaus, G.N., J. Org. Chem., (1975), 40 (7), 883-9.

Compounds that have at least two groups functional capable of forming reactive groups, which are capable of C-H insertion under reaction conditions is are referred to herein as coupling agents. Sayings coupling agents include alkyl- and aryl azides (R-N3), acyl azides (R-C (O) N3), azidoformates (R-O-C (O) -N3), phosphoryl azides ((RO) 2- (PO) -N3), phosphonic azides (R2-P (O) -N3) and silyl azides (R3-Si-N3). Preferably, the coupling agent is a poly (sulfinyl azide). Patent application from the USA 09 / 133,576, filed on August 13, 1998, and the WO 99/10424 published March 4, 1999, contain additional teachings regarding azides and their use for polymer modification.

When you react the poly (sulfonyl azide) with the resin propylene polymer, at least two separate polymer chains of propylene are advantageously bonded and the molecular weight of the polymer chain is increased. In the preferred case when the poly (sulfonyl azide) is a bis (sulfonyl azide) (hereinafter "BSA"), advantageously two polymer chains of propylene

The poly (sulfonyl azide) is any compound that has at least two groups sulfonyl azide (-SO2N3) reactive with the polymer of propylene Preferably the poly (sulfonyl azide) has a structure X-R-X in which each X is SO2N3 and R represents a hydrocarbyl, hydrocarbyl ether or group containing unsubstituted or inertly substituted silicon, having preferably enough carbon, oxygen or silicon atoms, preferably carbon, to separate the groups sulfonyl azide sufficiently to allow easy reaction between the propylene polymer and the sulfonyl azide, more preferably at least 1, more preferably at least 2, and most preferably at least 3 carbon, oxygen or silicon atoms, preferably carbon, between functional groups. While there is no limit to the length of R, each R advantageously has at least one atom of carbon or silicon between X and preferably has less than 50, more preferably less than 20, and most preferably less than 15 carbon, oxygen or silicon atoms. The groups that contain Silicon include silanes and siloxanes, preferably siloxanes. The inertly substituted expression refers to substitution with atoms or groups that do not interfere undesirably, in the coupling conditions, with the reaction (s) desired (s) or desired properties of polymers trailers that are obtained. Such groups include fluorine, ethers aliphatic or aromatic, siloxane as well as groups sulfonyl azide when more than two are to be joined polyolefin chains. R is suitably an aryl, alkyl group, arylalkyl, arylalkyl, silane, siloxane or heterocyclic and others groups that are inert and separate groups sulfonyl azide as described. Plus preferably R includes at least one aryl group between the groups sulfonyl, most preferably at least two aryl groups (such as when R is 4,4'-diphenyl ether or 4,4'-biphenyl). When R is an aryl group, it prefers that the group has more than one ring, as in the case of the naphthalen-bis (sulfonyl azides). Poly (sulfonyl azides) include compounds  such as 1,5-pentane-bis (sulfonyl azide), 1,8-octane-bis (sulfonyl azide), 1,10-decane-bis (sulfonyl azide), 1,10-octadecane-bis (sulfonyl azide), 1-octyl-2,4,6-benzene-tris (sulfonyl azide), 4,4'-diphenyl ether-bis- (sulfonyl azide), 1,6-bis (4'-sulfonazidophenyl) hexane, 2,7-naphthalen-bis (sulfonyl azide), and mixed sulfonyl azides of hydrocarbons chlorinated aliphatics containing an average of 1 to 8 chlorine atoms and from 2 to 5 sulfonyl azide groups per molecule and their mixtures Poly (sulfonyl azides) preferred include oxy-bis (4-sulfonyl azidobenzene), 2,7-naphthalen-bis (sulfonyl azido), 4,4'-bis (sulfonyl azido) biphenyl, 4,4'-diphenyl ether-bis (sulfonyl azide) Y bis (4-sulfonyl-azidophenyl) methane and their mixtures.

The sulfonyl azides are commercially available and conveniently prepared by reaction of sodium azide with sulfonyl chloride corresponding, although oxidation of the sulfonyl hydrazines with various reagents (acid nitrous, dinitrogen tetroxide, and tetrafluoroborate nitrosonium)

The following discussion, considering the mechanism of the coupling reaction, provides the inventors current theories, but you don't want to limit the scope of this invention. The sulfonyl azides break down of various ways, but for the practice of the invention, the reactive species that is believed to be singlet nitrene, as demonstrates by insertion in C-H links. Be indicates that thermal decomposition gives a sulfonyl nitrene singlet, intermediate, which will react easily by insertion into carbon-hydrogen bonds. The high temperatures necessary for the effective formation of sulfonyl nitrene are normally greater than 150 ° C. When using BSA, such as 4,4'-oxidibenzenesulfonyl azide (DPO-BSA) as a coupling agent, it is preferred avoid polymer current temperatures above 250 ° C while there is significant unreacted azide in the mixture of reaction.

The poly (sulfonyl azide) is mixed preferably, at least partially, with the polymer of propylene before the resulting mixture is heated to the maximum decomposition temperature of poly (sulfonyl) azide) By maximum decomposition temperature of the poly (sulfonyl azide) means that temperature at that a substantial percentage of the azide is converted to sulfonyl nitrene, eliminating nitrogen and more heat in the process. The decomposition temperature can be determined by calorimetry of differential scan (DSC). For example, a thermogram of differential scanning calorimetry (DSC) of the DPO-BSA shows no change in heat flow until that a maximum temperature of abrupt endothermic fusion is observed at 100 ° C. The baseline is flat again (no heat flow) until a wide exothermic maximum temperature is observed that starts at approximately 150ºC, maximum temperature at 185ºC (referred to herein as the temperature of maximum decomposition) and is completed at 210 ° C. The total amount of energy released due to the decomposition of sulfonyl groups Azide is 1,500 Joules / gram. Preferably, the poly (sulfonyl azide) is heated to at least the maximum decomposition temperature. Poly (sulfonyl) azides) used advantageously have a temperature of maximum decomposition greater than 150 ° C, preferably greater than 160 ° C, more preferably greater than 180 ° C.

The amount of poly (sulfonyl azide) is preferably at least about 50 parts per million in weight of the propylene polymer (ppm), more preferably at least about 75 ppm, more preferably at least about 100 ppm, and in some cases preferably at least  approximately 150 ppm In the practice of the invention, there is to avoid the formation of reticulated networks to a point that would result in non-malleable propylene polymer; for the therefore, the poly (sulfonyl azide) is preferably limited to that amount that results in propylene polymer with chain coupling or rheologically modified (but not substantially crosslinked), preferably less than 2,000 ppm, more preferably less than 1,500 ppm, most preferably less than 1,300 ppm of poly (sulfonyl azide) based on weight Total propylene polymer. Substantial crosslinking is characterized by the presence of gels of percentage in weight or size enough, so that the film's processing looks adversely affected. Such detrimental effects include increased operating voltage, presence of discontinuities or materials not dispersed in the film, return pressure increased, and / or partial plugging of the nozzle due to gels or black granules The amount to use depends on the mass flow melting of the starting and target propylene polymers and it Can be determined by the expert person.

The random or impact copolymer of propylene and the coupling agent are properly combined from any so as to result in the desired reaction thereof, preferably by mixing the coupling agent with the polymer under conditions that allow sufficient mixing before or during reaction to avoid unnecessary or undesirably amounts unequal, localized reaction. An undesirable amount is a amount that interferes with the purpose of the final product. In a preferred embodiment, the process of the present invention takes place in a single container, that is, the agent mixture coupling and the polymer takes place in the same container as  heating at the decomposition temperature of the agent coupling The container is most preferably an extruder double spindle, but preferably a single spindle extruder or advantageously a melt mixer, including a batch mixer The reaction vessel has more preferably at least two different temperature zones than that a reaction mixture would be passed.

In the most preferred embodiment, the copolymer of propylene and the coupling agent are physically mixed to a temperature that is low enough to minimize the reaction between the coupling agent and the polymer. Such physical mixture it can take place in any equipment, such as: V mixers, horizontal mixers with helical or vane belt, drums dump or extruders, which will mix the coupling agent and the propylene polymer. The term extruder is used in its broader meaning to include devices such as a device that extrudes pellets, as well as an extruder that produces the extruded to conform it in articles, such as films.

Preferably, this physical mixing takes place. in the initial stages of an extruder, most preferably a twin screw extruder. In particular, this embodiment can be practice simultaneously introducing the polymer resin of propylene and coupling agent, in the feed section  of an extruder. The extruder is configured to have a first section that physically mixes and transports the agent from coupling and polymer in a way that minimizes the reaction between the coupling agent and the polymer. The first section of transport is followed by at least a second section in which the coupling agent and the polymer and enough heat is added to cause a reaction significant between the coupling agent and the polymer.

In another embodiment, the mixture is achieved preferably with the polymer in a molten state or at least partially molten, that is, above the temperature of softening of the polymer, or in a dissolved or finely state dispersed instead of in the form of solid mass or in the form of particles Any mixing equipment is properly used in this embodiment, preferably equipment that provides sufficient mixing and temperature control in the same equipment, but it has advantageously practical place of this embodiment in devices Such as an extruder, melt mixer, conveyor pumping or a polymer mixing device such as a Brabender melt mixer. Although it is within scope of this embodiment that the reaction take place in a solvent or other medium, it is preferred that the reaction be in a phase in volume to avoid later stages for elimination of solvent or other medium.

The molten phase mixture is advantageous for forming a substantially uniform mixture of agent coupling and polymer before exposure to conditions in which a chain coupling takes place. Conveniently for this embodiment, the formation of a substantially uniform mixture takes place along a temperature profile within equipment, such as an extruder. The first zone is advantageously to a temperature at least the softening temperature of the (of the) polymer (s) and preferably less than the decomposition temperature of the coupling agents and the second zone being at a temperature sufficient for the decomposition of the coupling agent. Especially in the case of propylene polymers, most preferably they are exposed the propylene polymer (s) and the agent coupling to a mass current temperature profile melt ranging from 160 ° C to 250 ° C.

Those skilled in the art recognize that a polymer, or mixture thereof, typically melts above a temperature range instead of melting sharply at a temperature. For the practice of this embodiment, it is sufficient that the polymer is in a partially molten state. By comfort, you can approximate the temperature of this degree of fusion from the differential scanning calorimetry curve (DSC) of the polymer or mixture thereof, which has to be treated.

Conveniently, when there is a stage of extrusion of the melt between the production of the material of copolymer and its use, at least one stage of the process of the invention in the dough extrusion stage cast. The heat produced during the extrusion stage provides the energy necessary to cause the reaction between the coupling agent and the target polymer.

For all embodiments, a temperature of at least the decomposition temperature of the coupling agent is preferably maintained, for a time sufficient to result in the decomposition of at least sufficient coupling agent to avoid further unwanted reaction, preferably reacted at least 80, more preferably at least 90, most preferably at least 95 percent by weight of the coupling agent. Those skilled in the art understand that this time depends on whether the temperature is one at which the coupling agent decomposes slowly or one at which it decomposes very rapidly. Preferably, the time will be at least 5 seconds, more preferably at least 10 seconds to avoid unreacted coupling agent and subsequent undesirable reactions, or to avoid the need for possible destructively high temperatures, inconveniently. Conveniently, the reaction time is about 20
seconds.

Other thermoplastic polymers can be mixed with propylene polymers with the condition that they are achieved the desired properties of the foam. Examples of these include high and low density polyethylenes, aromatic interpolymers of ethylene vinyl, 1-polybutene, ethylene vinyl acetate copolymer, rubber ethylene-propylene, rubber styrene-butadiene, copolymer of ethylene-ethyl acrylate and the like, which can be mix in the above-mentioned propylene polymer, provided that the latter is the main component of the mixture resulting and the mixture is of uniform quality.

Mixtures can be prepared by any methods known in the art such as, for example, mixing dried in a pellet form in desired proportions followed by melt mixing in an apparatus such as an extruder of screw or a Banbury mixer. Dry, mixed pellets, can be processed directly in the molten state to a final foam in solid state. Mixtures can also be obtained by direct polymerization without isolation of the components of the mixture. Direct polymerization can use, for example, one or more catalysts in a single reactor or in two or more reactors in series or in parallel and vary at least one of the conditions of operation, choice of monomer and catalyst mixtures.

Various additives can be incorporated into the compositions or foams of the present invention. Additives include, without limitation, stability control agents, nucleating agents, inorganic fillers, conductive charges, pigments, dyes, antioxidants, acid scavenging agents, ultraviolet absorbers or stabilizers, retardants of the flame, treatment aids, extrusion aids, antistatic agents, adhesion additives (for example, polyisobutylene), anti-block additives, other polymers thermoplastics Some of the additives, such as fillers inorganic and conductive, they can also function as agents of nucleation and / or open cell promoters for foams. Examples of antioxidants are hindered phenols (such as, for example, Irganox ™ 1010) and phosphites (for example, Irgafos? 168), both brands of, and commercially available in, Ciba Geigy Corporation.

The additives are advantageously used in Functionally equivalent amounts known to experts in the technique For example, the amount of antioxidant used is that amount that prevents the polymer or the mixture of polymer undergoes oxidation at the temperatures and environment used during storage and final use of polymers. Such amount of antioxidant is usually in the range of 0.01 to 10, preferably 0.02 to 5, more preferably 0.03 to 2 per weight percent based on the weight of the polymer or polymer blend. Similarly, the amounts of any of the other additives Listed are functionally equivalent amounts.

The polymer compositions described previously they can be converted into foam products using Any of the conventional procedures. The products of foam include, for example, thermoplastic polymer foam extruded, extruded strand polymer foam, foam beads expandable thermoplastic, expanded thermoplastic foam beads and molten thermoplastic foam beads and various types of foams reticulated. Foam products can have any known physical configuration, such as sheet geometry, round, strand, stick, solid iron, laminated plate, joined strand iron, profiles and box-shaped. The products foam can be converted into manufactured items using any of the conventional methods or procedures. By For example, one can be used in the manufacture of such articles. any or more between expansion, bonding and welding, especially from expandable foam beads. They can also be molded expandable beads in any known configuration that employs foam products, which include but are not limited to, previous settings.

The stages of the training procedures of Foams are well known in the art. For example, as per exemplifies by the teachings of manufacturing procedures of polymer ethylene foam structures and processes of them are described in C.P. Park, "Polyolefin Foam", Chapter 9, Handbook of Polymer Foams and Technology, D. edition Klempner and K.C. Frisch, Hanser Publishers, Munich, Vienna, New York, Barcelona (1991), which is incorporated herein by reference.

The foams of the present invention may be substantially uncrosslinked. That is, the foam structure contains 50 or less, preferably 40 or less, more preferably 30 or less, even more preferably 20 or less, most preferably 10 or less weight percent gel based on the total weight of the foam or polymer, measured according to Method A of the ASTM D2765-84.

As an alternative, polymeric compositions they can be used for the manufacture of foams that are substantially crosslinked (that is, they contain more than 50 per weight percent gel based on total polymer weight, measured according to Method A of ASTM D2765-84) by the subsequent addition of any crosslinking agent known. The various crosslinking agents and their technologies are described in the art. Crosslinking can be induced by the addition of a crosslinking agent. Induction of crosslinking and exposure to elevated temperatures to effect foaming or expansion can take place simultaneously or sequentially If a chemical crosslinking agent is used, it incorporates into the polymeric material in the same way as the agent of chemical expansion. In addition, if a crosslinking agent is used chemical, the foamable molten polymeric material is heated or exposed to a temperature preferably less than 150 ° C to avoid the decomposition of the crosslinking agent or the expansion and to prevent premature crosslinking. If the radiation crosslinking, molten polymer material foamable is heated or exposed to a temperature preferably less than 160 ° C to prevent decomposition of the blown. The foamable polymeric fusion material is extruded or leads through a nozzle of desired shape to form a foamable structure The foamable structure is then reticulated and expands at an elevated temperature (typically, 150 ° C-250 ° C) such as in an oven to form a foam structure If radiation crosslinking is used, the foamable structure radiates to crosslink the material polymeric, which then expands at elevated temperature as described above. The present structure may be advantageously formed in thin sheets or plates according to the previous procedure using either crosslinking agents or radiation.

The foam and foam structures of the present invention are optionally obtained by a method of conventional extrusion foaming. The structure is prepared advantageously by heating the copolymer material or mixture to form a plasticized or fusion polymer material, incorporating therein an expanding agent to form a gel foamable, and extrude the gel through a nozzle to form the foam product Depending on the nozzle (with a number appropriate openings) and operating conditions, the product may vary from an extruded foam plate or bar, to from a bonded foam product to foam beads and eventually to chopped strands of foamable pearls. Before the mixed with the expanding agent, the polymeric material is heats at its temperature of, or above, its temperature of glass transition or melting point. The blowing agent is optionally incorporates or mixes with the polymeric material melted by any means known in the art such as with an extruder, mixer, kneader, or the like. He blowing agent is mixed with molten polymeric material to a high pressure sufficient to prevent expansion substantial of the copolymer melt material and disperse advantageously the blowing agent in it homogeneously. Optionally, a nucleating agent is mixed in the melt polymer or dry mix with the polymeric material before the fusion or plasticization. Before extruding the foamable gel to through the nozzle, the gel is typically cooled to a optimum temperature The foamable gel is typically cooled to a lower temperature to optimize the physical characteristics of foam structure This temperature, often referred to as the  foaming temperature, is typically above the glass transition temperature (Tg) of each of the polymer components or for those who have enough crystallinity, close to the maximum crystalline melting temperature (Tm) "Next" means a, above or below and depends largely where the stable foam exists. Temperature Desirably descends approximately 30 ° C below or above Tm and preferably within 10 ° C above or by under Tm. For the foams of the present invention, a optimum foaming temperature is in the range in which the foam does not collapse. The gel can be cooled in an extruder or another mixing device, or in separate chillers. The gel is extruded or transported then through a nozzle the desired shape at an area of reduced or lower pressure to Shape the foam structure. The lowest pressure zone is at a lower pressure than that in which the gel is maintained foamable prior to extrusion through the nozzle. The lowest pressure can be optionally superatmospheric or subatmospheric (empty), but is preferably at a level atmospheric. The preferred foam forming limit for Propylene copolymer materials containing elastomer is from 142 to 162 ° C, more preferably from 152 to 162 ° C.

In another embodiment, the foam structure resulting is optionally formed in the form of joined strands by extrusion of the polymer material through a multi-hole nozzle The holes are arranged such that contact between adjacent currents occurs of molten extruded material during the foaming process and the surfaces in contact adhere to each other with sufficient adhesion to give rise to a foam structure unitary. The streams of molten extruded material leaving the nozzle takes the form of threads or profiles, which are foamed, they join desirably, and adhere to each other to form A unitary structure. Desirably the threads or profiles united individuals must remain attached in a structure unit to prevent the delamination of the strand under the tensions found in the preparation, conformation, and use of the foam. The devices and methods for the production of foam structures in the form of bonded strands are shown in U.S. Pat. Nos. 3,573,152 and 4,824,720.

As an alternative, the foam structure resulting is conveniently formed by a procedure and apparatus accumulation extrusion, as seen in US Pat. Nos. 4,323,528 and 5,817,705. This device, commonly known as an "extruder-accumulator system" allows operating a procedure on an intermittent basis instead of continuous.

The foam structures present are also They can be shaped into foam beads suitable for molding in items by expanding previously expanded pearls that They contain a blowing agent. The pearls can be molded in the moment of expansion to form articles in various ways. Procedures for the preparation of articles of expanded pearl foam and beam foam items expanded molded in Plastic Foams, Part II, Frisch and Saunders, P. 544-585, Marcel Dekker, Inc. (1973) and Plastic Materials, Brydson 5th ed., P. 426-429, Butterworths (1989). Expanded and expandable pearls can be obtain by a batch or extrusion process, and they can be substantially crosslinked or uncrosslinked.

The discontinuous manufacturing process of expandable pearls is similar to the manufacture of polystyrene expandable (EPS). The resulting foam structure is formed in non-crosslinked foam beads suitable for molding in articles. Discrete resin particles, such as granules made from propylene copolymer material, obtained either by mixing the melt or preferably by mixing in reactor, impregnated with a blowing agent in a suspension aqueous or in an anhydrous state in a pressure vessel at a pressure and high temperature. In the case of the aqueous suspension, the (the) blowing agent (s) is introduced in the middle liquid in which the granules are substantially insoluble (such as water) at a high pressure and temperature, in an autoclave or Another pressure vessel. The granules are well discharged quickly to the atmosphere or to a region of reduced pressure to expand the granules into foam beads or cool and cool unload as pearls without expanding. In a separate stage, the unexpanded beads are heated to expand them, for example, with steam or with hot air. This procedure to obtain foams in pearl it shows well in U.S. patents 4,379,859 and 4,464,484.

Foam beads can also be prepared preparing a mixture of polymer blend compositions of the present invention, optionally crosslinking agent, and agent of chemical blowing in a suitable mixing or extruder device and forming the mixture in pellets, and heating the pellets, expand and optionally crosslink them.

In another process for manufacturing crosslinked foam beads suitable for being molded into articles, the mixtures of the invention are melted and mixed with a physical blowing agent in a conventional foam extrusion apparatus to form an essentially continuous foam strand. The foam strand is granulated or formed into pellets to form foam beads. The foam beads are then crosslinked by radiation. Then, crosslinked foam beads can be joined and molded into various articles, as described above for the other foam beads procedures. In U.S. Patent 3,616,365 and in the previous publication CP Park, p. 224-228, additional teachings of this procedure can be found
I lie.

Foam beads can be molded later by any means known in the art, such as loading the beads foam in the mold, compress the mold to compress the beads and heat the beads, as with steam, to perform the bonding and fusion of pearls to form the article. Optionally, the beads can be impregnated with air or other blowing agent to high temperature and pressure before loading into the mold. Additionally, the beads may optionally be heated before load. The foam beads are then conveniently molded. in blocks or articles formed by a suitable molding method known in the art. Some of the methods are described in the U.S. Pat. Nos. 3,504,066 and 3,953,558. Excellent descriptions of the previous molding procedures and methods are shown in C. P. Park, supra, page 191, pages 197-198, and pages 227-233, patents  of the United States 3,886,100, 3,959,189, 4,168,353 and 4,429,059.

Blowing agents useful for preparing foam structures of the present invention include agents inorganic, organic blowing agents and blowing agents Chemicals Suitable inorganic blowing agents include dioxide carbon, nitrogen, argon, water, air, oxygen, hexafluoride sulfur (SF6) and helium. Organic blowing agents include aliphatic hydrocarbons of 1 to 9 carbon atoms, alcohols aliphatic of 1 to 3 carbon atoms, ketones, and hydrocarbons fully or partially halogenated aliphatics of 1 to 4 atoms of carbon. Aliphatic hydrocarbons include methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane and neopentane. Alcohols Aliphatics include methanol, ethanol, n-propanol and isopropanol Total or partially aliphatic hydrocarbons halogenated include chlorocarbons, fluorocarbons and chlorofluorocarbons. Examples of fluorocarbons include fluoride from methyl, perfluoromethane, ethyl fluoride, 1,1-difluoroethane (HFC-152a), fluoroethane (HFC-161), 1,1,1-trifluoroethane (HFC-143a), 1,1,1,2-tetrafluoroethane (HFC-134a),  1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,3,3-pentafluoropropane, pentafluoroethane (HFC-125), Difluoromethane (HFC-32), perfluoroethane, 2,2-difluoropropane, 1,1,1-trifluoropropane, perfluoropropane, dichloropropane, difluoropropane, perfluorobutane, perfluorocyclobutane. Chlorocarbons and chlorofluorocarbons partially halogenated for use in this invention include methyl chloride, methylene chloride, ethyl chloride, 1,1,1-trichloroethane, 1,1-dichloro-1-fluoroethane (HCFC-141b), 1-Chloro-1,1-Difluoroethane (HCFC-142b), chlorodifluoromethane (CFC-22), 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123) and 1-Chloro-1,2,2,2-tetrafluoroethane (HCFC-124). The chlorofluorocarbons totally halogenated include trichloromonofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12), trichlorotrifluoroethane (CFC-113), dichlorotetrafluoroethane (CFC-114), chloroheptafluoropropane, and dichlorohexafluoropropane. Chemical blowing agents include azodicarbonamide, azodiisobutyronitrile, barium azodicarboxylate, N, N'-dimethyl-N, N'-dinitrosoterephthalamide, and benzenesulfonylhydrazide, 4,4-oxybenzene sulfonylsemicarbazide, and p-toluenesulfonylsemicarbazide, trihydrazinatriazine, and mixtures of sodium bicarbonate and acid citrus, such as the various products marketed with the name of HydrocerolTM (a product of Boehringer Ingelheim). Any of the above blowing agents can be used individually or in combination with one or more other agents of blown. Preferred blowing agents include isobutane, n-butane, carbon dioxide, HFC-152a, and mixtures of the foregoing.

The amount of blowing agent incorporated in molten polymeric material to prepare a polymeric gel Foam former is 0.05 to 5.0, preferably 0.2 to 3.0, and most preferably 0.5 to 2.5 moles-gram per kilogram of polymer

A nucleating agent is optionally added in order to control the size of the foam cells. Preferred nucleating agents include substances inorganic such as calcium carbonate, talc, clay, dioxide titanium, silica, barium stearate, calcium stearate, earth of diatoms, and mixtures of citric acid and sodium bicarbonate, and Similar. When used, the amount of nucleating agent employee advantageously ranges from about 0.01 to approximately 5 parts by weight per one hundred parts by weight of a polymer resin

In the manufacture of foams, it is added optionally a stability control agent (also known as permeability modifier) to the present foam to enhance dimensional stability. Preferred agents include amides and fatty acid esters of C10-24. Such agents are shown in the Patents. from the USA No. 3,644,230 and 4,214,054. Esters can also reduce static capacity during and after manufacturing of foam The most preferred agents include stearyl-stearamide, glycerol monostearate, glycerol monobehenate, and sorbitol monostearate. When use, said stability control agents are employed in a amount in the range from> 0 to about 10 parts per One hundred parts of the polymer.

The foams are optionally perforated to improve or accelerate the exchange of gas permeabilization in the that the blowing agent comes out of the foam and air enters the foam. U.S. patents Nos. 5,424,016, 5,585,058 and WO 92/19439 and WO 97/22455, provide excellent drilling information.

If desired, the foams of this invention may be subsequently treated by any means known to increase the open cell content in the foam. Such post-treatment methods include, but are not limited to, mechanical compression of the foam and expansion of the foam by exposure to steam or hot air.

The foams of the present invention have generally a density less than 700, preferably less than 500, more preferably less than 250 kg / m 3, and even more preferably less than 100 kg / m3, most preferably 5 to 70 kilograms per cubic meter (according to ASTM standard D3575-93, Suffix W, Method B). Foams can be micromolecular (that is, with a cell size of less than about 0.05 mm, preferably about 0.001 mm, at about 0.05 mm) or macromolecular (ie size cell of about 0.05 mm or more). Macromolecular foam It has an average cell size of about 0.05 to about 15, preferably from about 0.1 to about 10.0, and more preferably from about 0.1 to about 5 millimeters, preferably 0.2 to 2.0, and more preferably 0.2 to about 1.8 mm, measured according to the procedure of the ASTM standard D3576-77. In general, the foams have a size medium cell that ranges from 0.001 to 10.0 mm.

The foams of the present invention exhibit preferably excellent dimensional stability. Foams preferred recover 80 percent or more of the initial volume when It is measured one month after an initial volume measurement within 30 seconds after foam expansion. The volume is measured by a suitable method such as cubic displacement of water.

The foams of the present invention have a open cell content ranging from 0 to 100 percent of volume based on total foam volume, as measured by ASTM procedure D2856-94, depending on the component selection and variations of the conditions of process. Foams with an open cell content of 20 volume percent or less generally fall into a known type as closed cell foams. Those known as cell foams open typically have an open cell content greater than 20, preferably greater than 40, and more preferably greater than 50 percent volume. The open cell content is desirably 100 percent volume or less, preferably 95 volume percent or less, and more preferably 90 percent of volume or less.

The foams preferably have a hardness Asker-C of <80, desirably <75, and preferably <70. The hardness of the foams is measured using a Asker-C hardness tester for cellular and spun rubber according ASTM D2240-97 standard measured in the direction of extrusion, using a spherical indenter of 5 mm in diameter.

According to very preferred embodiments, the foam comprises a modified or coupled rhetoric propylene impact copolymer in the reactor and has a density in the range of 50 kg / cm3 or less, and preferably
40 kg / m3 or less, and has an Asker-C hardness of? 35 and more preferably? 30, measured in the extrusion direction.

According to other very preferred embodiments, the foams of the present invention comprise a copolymer of impact of modified or coupled rheology propylene on the reactor and has a density in the range of 50 kg / cm3 or less, and preferably 40 kg / m 3 or less, and have preferably a Compressive Strength determined according to ASTM 3575 measured in the extrusion direction (in kPa (pounds per square inch, psi) for 25% compression) of ≤ 103 kPa (15 psi), more preferably ≤ 83 kPa (12 psi).

If the foam is in the form of a sheet or plate, has a thickness of generally ≥ 0.5 mm, preferably ≥ 1 mm, and a width of generally ≥ 5 mm, preferably ≥ 10 mm. As used herein memory, "thickness" of a sheet or foam sheet refers to its smallest cross-sectional dimension (for example, measured from a planar surface to a planar surface opposite). When the foam is present as a round or roller, has a diameter of generally ≥ 5 mm, preferably ≥ 10 mm.

The foams of the present invention can be use in any application where currently used open and closed cell density and content foams comparable. Such applications include, without limitation, packaging of mattresses (e.g. corner blocks, clamps, flanges,  flexible bags, bags, wrappers, covers, interpeliculation, encapsulation) of electronic products finished such as computers, televisions and utensils kitchen; packaging or protection of materials or devices explosives; handling (trays, handling boxes, box supplements, food box inserts, and dividers, ducts, filling, plates, and part separators); workstation accessories (aprons, table covers and benches, carpets, cushions); automotive (interior roof, absorption of impacts on bumpers or doors, carpet bases, acoustic isolation); flotation (for example, life jackets, vests and belts); sports and leisure (for example, mats gym, bodyboards); thermal insulation such as that It is used in building and construction; sound insulation (by example, for building and construction applications); together, sealed washers; sound attenuation for printers and typewriters; filling of monitor housings; filler missile containers; holds military pods; blocking and reinforcement of various items in transport; conservation and packaging; automotive vibration pads; seals; medical devices, skin contact pads; paddles padded and vibration isolation pads.

In another aspect, the polymer compositions of This invention can be used to make foamed films. The foamed film of the present invention may be a sheet monolayer or multilayer. Preferably, the sheet according to the invention has a thickness of 0.0127-0.254 mm (0.5 to 10 mils). The film of the invention may be printed. The foamed film is especially suitable for use as a label or in thermoformable articles of manufacture. To get foamed film structures, blowing agents can be used Physical or chemical A multilayer film of the invention comprising one or more foamed layers comprising the polymeric compositions as defined herein, is obtainable according to methods known in the art, for example, using a co-extrusion procedure.

The label film can be built to from rolls of printed film, with grooves in width, with labels attached to a container, for example a bottle, using Conventional adhesives or adhesives known in the industry. In addition, the sheets of this invention may be printed, coated with pressure sensitive adhesives, laminated to remove papers or films and apply them to bottles, containers or other surfaces using conventional sensitive techniques the Pressure.

The above list only illustrates a number of suitable applications. Those skilled in the art can view easily additional applications without departing from the reach or spirit of the present invention.

Examples

The following examples are to illustrate this invention and do not limit it. The relationships, parts and percentages They are by weight, unless otherwise indicated. For the examples then, unless otherwise indicated: the flow rate of melt (MFR) was measured according to ASTM D 1238, at a temperature of 230 ° C under a weight of 2.16 kg.

Dow C105-02 polypropylene, a propylene impact copolymer produced inside the reactor that contains about 18 percent units derived from ethylene and having an elastomer content of about 26 percent (ICP-1) had rheology modified with 225 ppm of 4-4'-oxibis (azide of benzenesulfonyl) to increase the toughness of the melt, under the following conditions: temperature bar (ºC): 25, 189, 234, 240, 244, 244, 229, 240, nozzle temperature: 246 ° C; nozzle pressure: 5012-5095 kPa (727-739 psi); melting temperature: 274 ° C; RPM of screw: 435; speed: 99.8 kg / h (220 lb / h). The comparisons they were made with PROFAX * PF814 of high dough toughness PP cast (homopolymer). PROFAX is a trademark of Montell Company. The modified rheology ICP-1 (rICP-1) exhibited higher and lower toughness module compared to the PF814 PP.

Dow polypropylene DS6D82, a random copolymer of propylene containing approximately 3.2 percent of ethylene units (RCP-1) had rheology modified with 4,4'-oxybis (azide of benzenesulfonyl) 900 ppm under the following conditions: temperatures (° C): 27, 156, 210, 226, 230; nozzle pressure: 1655 kPa (240 psi); melting temperature: 230 ° C; RPM of screw: 353; speed: 27.2 kg / h (60 lb / h) to give rRCP-1.

Dow polypropylene 6D70K, a random copolymer of propylene containing approximately 3.2 percent units ethylene derivatives (RCP-2) had rheology modified with 1000 ppm of 4,4'-oxybis (azide of benzenesulfonyl) under the following conditions: temperatures (ºC): 27, 156, 215, 229, 233, nozzle pressure: 1793 kPa (260 psi); Screw RPM: 408; speed: 27.2 kg / h (60 lb / h) to give rRCP-2.

Dow polypropylene C107-04, a propylene impact copolymer produced inside the reactor containing about 8 percent units derived from ethylene and having an elastomer content of about 16 percent (ICP-2) had rheology modified with 200 ppm of 4-4'-oxibis (azide of benzenesulfonyl), under the following conditions: temperatures (° C): 25, 25, 17, 153, 200, 240, 260, 260, 260; nozzle pressure: 2641-2910 kPa (3 83-422 psi); melting temperature: 250 ° C; RPM of screw: 220; speed: 59.0 kg / h (130 lb / h) to give rRCP-2.

one

Foam preparation

For the production of foam samples a from PROFAX PF814 and polypropylene copolymers of modified rheology as written above a tandem extrusion system consisting of a double extruder 34mm diameter co-rotational spindle (extruder mixing) that feeds a 40mm single screw extruder of diameter (cooling extruder). The polymer pellets are fed into the hopper of the twin screw extruder. Was injected blowing agent (BA) (isobutane) in the twin screw extruder. 0.25 weight percent talc was used as a nucleant. Polymer loaded with blowing agent was compressed and then it fed the spindle extruder and cooled to a temperature optimized and then extruded through a nozzle of 2 mm diameter bar. Foaming conditions, as well as the properties of the foam are incorporated in the tables to continuation. C-1 to C-4 are examples comparatives and Ej-1 to Ej-9 are inventive examples.

Rheology propylene copolymers modified expanded successfully to obtain low foams density. Stable foam was obtained at a BA level that could Increase from 8.2 to 12.00 parts by weight. The rICP's gave as a result a significantly lower foam density and a softer foam of smaller cell size as well as smaller remnant compression In addition to the blowing efficiency (density of theoretical foam if all expanded blowing agent divided by the actual density of the foam multiplied by 100%) for the foam of the invention was significantly greater than for foam comparative (80 percent or more versus 72 percent). The CPR resulted in a significantly lower foam density, a softer foam, as well as less compression remaining, a greater blowing efficiency compared to foam comparative

TABLE 1A

2

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X / Y / Z address according to ASTM 3576, where Z is the address of
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TABLE 1B

3

Claims (14)

1. A foam comprising a material of propylene copolymer comprising at least 50 percent in weight of units derived from propylene, based on total weight of the propylene copolymer material, and units derived from ethylenically unsaturated comonomers and having a flow rate of melt in the range of 0.5 to 8 g / 10 min, a toughness of the melt of at least 5 cN, and a stretching capacity of the melt of at least 20 mm / s. 2. A foam according to claim 1, in the that the propylene copolymer material has a mass flow rate melted in the range of 0.6 to 5 g / 10 min, a toughness of the melt of at least 7 cN, and a stretching capacity of the melt of at least 30 mm / s. 3. A foam according to claim 2, in the that the propylene copolymer material has a mass flow rate melted in the range of 0.6 to 3.5 g / 10 min, a toughness of the melt of at least 10 cN, and a stretching capacity of the melt of at least 40 mm / s. 4. A foam according to claim 1, 2 or 3, in which the ethylenically unsaturated comonomer of the material of Propylene copolymer is selected from the group consisting of ethylene, 1-olefins from C_ {4} -C_ {10} and dienes of C_ {4} -C_ {10}. 5. A foam according to any of the previous claims, wherein the copolymer material of propylene comprises a homopolymer of propylene or a copolymer of random or block propylene as a continuous phase and a phase elastomer uniformly dispersed therein. 6. A foam according to any of the claims 1-4, wherein the material of propylene copolymer comprises a propylene copolymer at random, chance, fate. 7. A foam according to claim 5, in the that the propylene copolymer material is a material of modified rheology propylene copolymer. 8. A foam according to claim 6, in the that the random propylene copolymer is a copolymer of randomized propylene of modified rheology. 9. A foam according to any of the previous claims, which has a density of less than 250 kg / m 3. 10. A foam according to claim 9, which It has a density in the range of 5 to 70 g / m3. 11. Article comprising a foam according to any of the preceding claims. 12. A procedure to obtain a foam, which comprises converting a propylene copolymer material that comprises at least 50 percent by weight of units derived from propylene, based on the total propylene copolymer material, and units derived from ethylenically unsaturated comonomers and which have a melt flow rate in the range of 0.5 to 8 g / min, a melt toughness of at least 5 cN, and a capacity to stretch the melt of at least 20 mm / s, optionally mixed with a nucleating agent, in a melt polymer, introduce, at a high pressure, at least one agent blowing into the polymer melt to form a gel foamable, cool the foamable gel and extrude the foamable gel in a region of lower pressure to form a foam. 13. A procedure to obtain a foam in shape of thermoplastic foam beads, which comprises converting a propylene copolymer material comprising at least 50 per percent by weight of units derived from propylene, based on the Total propylene copolymer material and units derived from ethylenically unsaturated comonomers and having a flow rate of melt in the range of 0.5 to 8 g / 10 min, a toughness of the melt of at least 5 cN and a stretching capacity of the melt of at least 20 mm / s, optionally mixed with a nucleating agent, in a polymer melt, cool and granulate the polymer melt to form particles discrete resin, create a suspension dispersing the resin particles in a liquid medium in which they are substantially insoluble, introduce at least, under pressure and high temperature, a blowing agent in the suspension for form resin particles that have a blowing agent built into them and quickly download the product in a atmosphere that promotes the conversion of the product into pearls of foam. 14. Expandable composition comprising a propylene copolymer material comprising at least 50 per percent by weight of units derived from propylene, based on the Total weight of the propylene copolymer material, and units derived from ethylenically unsaturated comonomers and having a melt flow rate in the range of 0.5 to 8 g / 10 min, a melt toughness of at least 5 cN, and a capacity of stretching of the melt of at least 20 mm / s, optionally mixed with a nucleating agent and a blowing agent.